"A lot of cities are putting in things such as low-flow diversions so that during the dry months, polluted urban runoff can be diverted to the sewer system where it gets treated," she said.

"We also saw different ordinances go into place that deal with `low-impact development' so that water from development projects is kept on-site instead of running off and picking up pollution."

Heal the Bay found some stretches of very good to excellent water quality in all Santa Monica beach locations from Castle Rock Beach to Marina del Rey.

In all, six local beaches made it to the "Honor Roll," after consistently getting grades of A or A+.

However, L.A. County also accounted for seven of the 20 most polluted beaches in the state. But of the 20 best, only two were in L.A.

The list of "Top 10 Beach Bummers" includes: Topanga State Beach at the creek mouth and no fewer than four beaches in Malibu, namely: Puerco Beach, Dan Blocker, Surfrider and Escondido, which are located next to developed areas with no sewer infrastructure.

All told, 11 local beaches received a grade of F, up from last year's nine.

Avalon Beach in Catalina is the dirtiest, because of outdated and leaking sewer lines.